The present invention relates generally to the field of data storage hardware and software, and more particularly to configuring a secondary storage system for data mirroring.
Disaster recovery systems typically address two types of failures, a sudden catastrophic failure at a single point in time or data loss over a period of time. In the second type of gradual disaster, updates to volumes may be lost. To assist in recovery of data updates, a copy of data may be available from a remote location. Such dual copies are typically made as the application system is writing new data to storage within a primary computing system. Data mirroring is one copy technology for maintaining remote copies of data at a secondary site or in a secondary storage system. In data mirroring systems, data is maintained in storage volume (e.g., disk) pairs. A volume pair is comprised of a storage volume within a primary computing system and a corresponding volume in a secondary storage system that includes an identical copy of the data maintained in the primary volume. Primary and secondary control units, also known as storage controllers or enterprise storage servers, may be utilized to enable more direct control of communications and transfers of data between the primary and secondary storage devices.
Data mirroring differs from data backup. Data backup saves a copy of data that is unchanged for a long period of time. Data mirroring occurs frequently and can be constrained to write activity, such as new data or updated data. In addition, mirroring does not require copying an entire data set or file, just the portions of data that are created or updated are written to storage. Data may be stored as discrete entities, such as tracks, extents, blocks, etc. Therefore, the current version of the data on a secondary storage system is relatively recent. Data mirroring can occur asynchronously to minimize write delays within a storage system of the primary computing system. As such, asynchronous data mirroring can achieve a relatively small recovery point objective (RPO) value. A RPO value is a maximum, targeted, period of time, as defined by a user (i.e., client), during which data mirrored to a secondary storage system is out-of-sync with the data stored within the primary computing system.